This round basin is designed to fit over the toilet seat. Sitz bath liquid is placed in the bag and can flow into the basin and overflow at the back into the toilet. This is a convenient way to soak the perineum in herbal solution or other solution.
The top rim dimensions are 14 1/2" round and the inner rim dimensions are 9 3/4" x 10 3/4". The basin is 4" tall. The inner rim is what would need to fit inside your toilet seat. The basin may not fit inside some toilet seats. It might fit inside the toilet bowl without the seat, but you should measure it.
Available in graphite color (different than the photo).